Estimate the pharmacokinetic paramaters of a single i.m. injection of testosterone 7-H3 enanthate (tracer) with and without cold testosterone enanthate (T.E.) (so that total mass is 200mg.) (7-10 subjects). Determine the plasma appearance and disapperance of 3-H T.E. and its metabolic products, 3-H- testosterone and 3-H-estradiol. Calculate plasma clearance rate and urinary excretion rate of T.E. and its labelled metabolites. Estimate plasma to tissue transport rates and conversion rates of testosterone to estradiol. Validate kinetic data obtained from (1) using a single intravenous tracer injection of labeled T.E. with and without a single intramuscular injection of cold T.E. (7-10 subjects). Characterize in detail the changes in T.E., bound and free testosterone, bound and free estradiol, and LH and FSH after a single infection of 200mg of cold T.E. (7-10 subjects).